Field of the Invention
The present invention relates to a gas diffusion layer with flowpaths. In particular, the present invention relates to a gas diffusion layer with flowpaths that exhibits superior power generation capability and comprises a flow channel of low height.
Background Information
Fuel cells that are capable of operating at ambient temperature and yielding high output density have drawn attention lately as power sources for electric vehicles, stationary power sources, and the like in response to social demands and trends arising from energy- and environment-related problems. The fundamental electrode reaction product of fuel cells is water, making such cells a clean power generation system that exhibits almost no deleterious effects upon the global environment. In particular, polymer electrolyte fuel cells (PEFCs) show promise as power sources for electric vehicles due to their ability to operate at comparatively low temperatures. Polymer electrolyte fuel cells are composed of layers of multiple individual cells that serve to generate power. Each of the individual cells is provided with a membrane-electrode assembly (MEA) comprising a polymer electrolyte membrane and a pair of catalyst layers and a pair of gas diffusion layers (GDLs) sequentially formed on both sides of the membrane. The MEAs of the individual cells are electrically connected to the MEAs of adjacent individual cells via separators. The layered individual cells make up a fuel cell stack. The fuel cell stack functions as a power generation means that can be used in a variety of applications.
As discussed above, the separators in such fuel cell stacks serve to electrically connect adjacent individual cells. In addition, gas flow channels are typically provided between the surfaces of an MEA and the opposing separators. These gas flow channels serve as means for supplying fuel gas and oxidant gas to the anode and the cathode, respectively. Typically, the separators are manufactured by pressing metal plates or carving plates of graphite.
To explain the power generation mechanism of a PEFC in brief, a fuel gas (such as hydrogen gas) is supplied to the anode side of the individual cell, and an oxidant gas (such as air or oxygen) is supplied to the cathode side. This results in the electrochemical reactions represented by the following formulas occurring at the anode and the cathode, thereby generating power.[Formula 1]Anode reaction: H2→2H++2e−  (1)Cathode reaction: 2H+2e−+(½)O2→H2O  (2)
The GDL requires a gas supply mechanism for efficiently diffusing and supplying the fuel gas and oxidant gas to the catalyst layers in order to bring about the electrochemical reactions described above; various such mechanisms have been proposed. For example, Japanese Laid-Open Patent Application No. 2009-272101 discloses a fuel cell in which electroconductive members (wires) for forming a specific macro space are disposed between the anode catalyst layer and a fuel supply section or the cathode catalyst layer and an oxidant supply unit so as to contact the catalyst layer and the supply section. That is, Japanese Laid-Open Patent Application No. 2009-272101 discloses forming a flow channel using electroconductive wires and rapidly expelling gas generated at the anode and water generated at the cathode through this macro space to the exterior, enabling electrical resistance to be reduced.